Packaging Apparatus and Method of Making Packages

ABSTRACT

A packaging apparatus including a cutting device, the cutting device comprising an elongate holder, an elongate knife having an elongate cutting edge, and a heat seal device located on the elongate holder on opposed sides of the knife, the heat seal device comprising a pair of elongate pressure strips projecting outwardly from the elongate holder, each pressure strip extending along a respective side of the knife, wherein each pressure strip comprises an elongate bar mounted for sliding movement in a respective slot in the elongate holder, the sliding movement varying the distance an outer edge of the elongate bar projects from the elongate holder, and a biasing element within the respective slot, the biasing element engaging an inner edge of the elongate bar and arranged to bias the elongate bar outwardly of the slot. A packaging method is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a US 371 National Stage Application fromPCT/EP2012/072651 filed Nov. 14, 2012, which claims priority to GB1119863.7 filed Nov. 17, 2011, now GB Patent 2496645, issued Apr. 9,2014, the technical disclosures of which are hereby incorporated hereinby reference.

The present invention relates to packaging apparatus and to a method ofmaking packages.

It is known to employ vertical form, fill, and seal (VFFS) packagingapparatus to produce packages, in the form of bags, pillow packs orpouches of products, such as snack foods. A tubular film, having beenformed from a roll of packaging film of heat sealable plastic materialwhich has been longitudinally sealed, is fed intermittently through ajaw device. The film forms a flattened tube at the jaw device. The jawdevice forms a pair of vertically spaced hermetic heat seals extendingtransversely across the tube, the seals being located between verticallyadjacent packages. The jaw device also cuts through a middle portion,located between the hermetic seals, extending across the tube whichseparates a lower sealed package containing the packaged product from anupper unsealed package.

In this way, a lower hermetic seal forms the upper seal of the lowerpackage, and an upper hermetic seal forms the lower seal of the upperpackage. The upper package is then filled with product, the tube isadvanced downwardly through the jaw device, and then the cycle isrepeated when the upper edge of the upper package, and the lower edge ofthe following package, is disposed between the jaws of the jaw device.

There are several known principles of operation of such jaws of avertical, form, fill, and seal (VFFS) packaging apparatus. One class ofjaw devices utilises a continuous rotary jaw motion, which isillustrated with reference to FIG. 1.

Referring to FIG. 1, in such a jaw device 10, a knife 12 is disposed onone side of the flattened, longitudinally sealed tube 14, and a hardenedreaction pad or anvil 16 is disposed on the opposite side of the tube14, with the tube located between the knife 12 and anvil 16. The knife12 is urged under pressure against the anvil 16 to cut through the filmof the tube 14, trapped between the knife blade 18 and the anvil 16, bya pressured crush-cutting action.

The knife 12 and the anvil 16 both rotate in phase and in oppositerotational directions as shown by the arrows in FIG. 1 so that the knife12 and the anvil 16 engage so as to cut packaging film material, in theform of a flattened tube as described below, centrally locatedtherebetween.

The knife 12 is rotated about an axis X orthogonal to the longitudinaldirection L of the tube 14 and parallel to the surface of the anvil 16and the cutting edge 20 of the blade 18. Although not illustrated,plural knives 12 may be mounted about a common shaft disposed along axisX and mutually angularly separated, so that for each cycle of rotationof the common shaft, plural cuts are made by respective knives 12.Plural anvils 16 would be correspondingly provided.

The elongate knife 12 is mounted in an elongate holder 21 in the form ofa mounting block. The lower portion of the knife 12 is received in anelongate recess 30 in the elongate holder 21 and securely fixed therein.The cutting action of the knife 12 is progressive, so that during thecontinuous rotation of the knife 12 in holder 21, initially onelongitudinal end of the knife 12 first contacts the anvil 16 andsubsequently the contact point therebetween progresses along the cuttingedge 20 of the blade 18 towards the other longitudinal end of the knife12. To achieve such progressive cutting action, the cutting edge 20 ofthe blade 18 is ground at an angle α to the plane of the knife 12.Typically, the angle α is 2 degrees. Accordingly, as the rotary contactprogresses, the whole width of the flattened tube 14 is not cut throughsimultaneously, but instead point contact of the knife blade 18transitions across the tube 14 as the rotary action progresses. Theprogressive cutting action is similar to that of a rotary blade of acylinder lawnmower.

Elongate heat seal devices 26, 28 are disposed either in the anvil 16and/or in the elongate holder 21 for the knife so that transversehermetic seals 32, 34 are formed in the flattened tube 14 on oppositesides of the transverse cut 36 made by the knife 12. The heat sealdevices 26, 28 may take a number of forms, typically transverselyextending mating ridges and grooves formed in the opposed surfaces ofthe anvil 16 and the elongate holder 21.

The knife 12 and the heat seal devices 26, 28 are mutually parallel andalso parallel to the sides 40, 42 of the elongate holder 21 which isorthogonal to the longitudinal direction L. Thus, when the longitudinaldirection is conventionally oriented vertically, the knife 12 and theheat seal devices 26, 28 are horizontal.

The known rotary jaw device provides an effective heat sealing andcutting mechanism, which reliably forms hermetic seals at the oppositeends of a package and with adjacent packages being reliably separated bythe action of the knife.

However, there is an increasing need for product manufacturers to reducethe amount of packaging material associated with their products, and inparticular not only to reduce packaging costs but also to reduce thecarbon footprint, expressed in tonnes of carbon dioxide emissions, ofthe packaging material and/or the packaging operation.

The known rotary jaw device forms hermetic seals which are rather wide,in the longitudinal direction of the tube, and also there is materialwastage between adjacent hermetic seals, because a portion of the filmmaterial of the tube which is cut through by the rotary cutting actionof the knife must be provided between the adjacent hermetic seals.

Accordingly, there is a need in the art for a rotary jaw device for apackaging apparatus, and to a method of making packages, which canpermit the amount of packaging material to be reduced, together with theassociated packaging costs and carbon footprint, i.e. carbon dioxideemissions, while still achieving effective hermetic seals at theopposite ends of a package.

The present invention aims at least partially to meet this need.

The present invention accordingly provides a packaging apparatus adaptedfor forming pillow packs of film material, the apparatus including acutting device, the cutting device comprising an elongate holder, anelongate knife having an elongate cutting edge, and a heat seal devicelocated on the elongate holder on opposed sides of the knife, the heatseal device comprising a pair of elongate pressure strips projectingoutwardly from the elongate holder, each pressure strip extending alonga respective side of the knife, wherein each pressure strip comprises anelongate bar mounted for sliding movement in a respective slot in theelongate holder, the sliding movement varying the distance an outer edgeof the elongate bar projects from the elongate holder, and a biasingelement within the respective slot, the biasing element engaging aninner edge of the elongate bar and arranged to bias the elongate baroutwardly of the slot, wherein the elongate bar is rigid and has athickness of from 1.5 to 2.5 mm, and wherein the biasing elementcomprises an elongate strip of elastic resilient material which has anupper surface which mates with the inner edge of the elongate bar, andan anvil mounted in opposition to the elongate holder, so that theelongate holder and the anvil comprise opposed jaws of a jaw device, theanvil having a reaction surface for the cutting action of the knife andfor the pressure strips.

Preferably, the elongate bar is composed of a metal, such as stainlesssteel.

Optionally, the outer edge of the elongate bar has a convexcross-section. Typically, the convex cross-section is arcuate, andoptionally the arcuate cross-section has a radius of from 0.75 to 1.25mm.

Preferably, the elongate bar is captive in the elongate holder.Optionally, the elongate bar has a first coupling element located ateach longitudinal end of the elongate bar which couples with a secondcoupling element located at each longitudinal end of the slot, the firstand second coupling elements retaining the elongate bar captive in theelongate holder. Preferably, the first coupling element comprises a maleelement and the second coupling element comprises a channel extendingalong the sliding direction of the elongate bar.

The elastic resilient material preferably comprises an elastomericpolymer. Typically, the elongate strip of elastic resilient material hasa circular cross-section.

In one embodiment, the elongate knife is mounted on and projectsoutwardly from the elongate holder.

In one preferred embodiment, the holder is mounted on a mounting supportadapted to rotate about a rotational axis, the knife is planar, theelongate cutting edge is parallel to the plane of the knife and theplane of the knife is inclined to the rotational axis. Preferably, thecutting edge extends along a centre of the knife. Typically, the knifehas a thickness of from 1 to 3 mm.

Preferably, the holder is mounted on a mounting support adapted torotate about a rotational axis, the elongate cutting edge is parallel tothe plane of the knife and the plane of the knife is inclined to therotational axis and the knife and anvil are mutually arranged so that asthe knife rotates by rotation of the elongate holder, the cutting edgeof the knife progressively contacts the reaction surface with a contactpoint therebetween moving longitudinally along the cutting edge.

Preferably, the anvil comprises a heater for heating the reactionsurface.

The packaging apparatus of the invention may be particularly adapted forforming pillow packs of film material.

The present invention further provides a method of making packages,wherein the packages are pillow packs of film material, the methodcomprising the steps of:

-   -   a. providing a flattened tube of packaging film;    -   b. providing a cutting device mounted in opposition to an anvil        so that the cutting device and the anvil comprise opposed jaws        of a jaw device, the cutting device having an elongate knife        with an elongate cutting edge, a pair of elongate pressure        strips projecting outwardly from an elongate holder, each        pressure strip extending along a respective side of the knife,        wherein each pressure strip comprises an elongate bar mounted        for sliding movement in a respective slot in the elongate        holder, the sliding movement varying the distance an outer edge        of the elongate bar projects from the elongate holder, and a        respective biasing element within the slot, the biasing element        engaging an inner edge of the elongate bar and arranged to bias        the elongate bar outwardly of the slot, wherein the biasing        element comprises an elongate strip of elastic resilient        material, wherein the elongate bar is rigid and has a thickness        of from 1.5 to 2.5 mm, and the anvil having a reaction surface        for the cutting action of the knife and for the pressure strips,        at least the reaction surface for the pressure strips being        heated;    -   c. locating a portion of the flattened tube between the cutting        device and the anvil;    -   d. relatively moving the cutting device and the anvil together;    -   e. cutting through the portion of the flattened tube between the        cutting device and the reaction surface of the anvil by the        cutting action of the knife; and    -   f. pressing the pressure strips against the heated reaction        surface thereby simultaneously heat sealing together opposed        sides of the flattened tube to form an elongate transverse        hermetic seal in the vicinity of each cut end of the flattened        tube, during the pressing action each elongate bar sliding        rearwardly in the respective slot against the bias of the        biasing element within the slot.

Typically, the cut edge of each package is 0.5 to 1.5 mm from thehermetic seal, more typically about 1 mm from the hermetic seal.Typically, the hermetic seal has a width of from 1 to 4 mm, moretypically from 1 to 2 mm.

Preferably, the packages are pillow packs of film material, andtypically the packages contain snack food.

Embodiments of the present invention will now be described by way ofexample only with reference to the accompanying drawings, in which:

FIG. 1 is a schematic side view of known rotary jaw device for apackaging apparatus;

FIG. 2 is a schematic section through a side of a rotary jaw device fora packaging apparatus in accordance with an embodiment of the presentinvention;

FIG. 3 is an enlarged schematic section through the cutting and heatsealing assembly and opposed anvil used in the rotary jaw device of FIG.2;

FIG. 4 is a schematic section on line A-A through the cutting and heatsealing assembly of FIG. 3;

FIG. 5 is a schematic plan view of the cutting and heat sealing assemblyof FIG. 3; and

FIG. 6 is a schematic side view of a pair of packages produced by therotary jaw device of FIG. 2.

FIGS. 2 to 5 illustrate a preferred embodiment of a rotary jaw devicefor a packaging apparatus according to the present invention, which hasa continuous rotary jaw motion. The device is structured and operates ina manner similar to that of the known device of FIG. 1 except that thestructure of the mounting block, the knife and the heat sealing devicesis significantly modified to achieve the desired reduction in the amountof packaging material required to form packages. The cutting and heatsealing assembly and the anvil both rotate in phase and in oppositerotational directions as shown by the arrows in FIG. 2 so that the knifeand the anvil engage so as to cut the film material centrally locatedtherebetween. The film material is intermittently advanced in thelongitudinal direction L.

In the jaw device 110 of FIG. 2, a knife 112 is disposed in a cuttingand heat sealing assembly 111 on one side of a flattened, longitudinallysealed tube 114 of packaging film to form packages 115, similar to theknown device of FIG. 1. One package 115 is shown in FIG. 2. A hardenedreaction pad or anvil 116 is disposed on the opposite side of the tube114, with the tube 114 located between the knife 112 and anvil 116. Theknife 112 is urged under pressure against the anvil 116 to cut throughthe film of the tube 114, trapped between the knife blade 118 and theanvil 116, by a pressured crush-cutting action.

In the illustrated embodiment, the elongate knife 112 is mounted on andprojects outwardly from the elongate holder.

The knife 112 is rotated about an axis X orthogonal to the longitudinaldirection L of the tube 114 and parallel to the surface of the anvil 116and the cutting edge 120 of the blade 118. The cutting and heat sealingassembly 111 holding the knife 112 is mounted about the axis, forexample to a shaft disposed along the axis, by a mounting support 111.The anvil 116 is similarly is rotated about an axis Y.

As shown particularly in FIGS. 3 and 5, the elongate knife 112 ismounted in an elongate holder 121 in the form of a mounting block. Forclarity of illustration, some dimensions and angles are exaggerated inFIGS. 3 and 4. Typically, the width of the knife (dimension a in FIGS. 3and 5) is from 1 to 3 mm, most typically 2 mm, and the cutting edge 120is centrally located along the entire length of the blade 118 of theknife 112.

In the illustrated embodiment, the elongate knife 112 is mounted on andprojects outwardly from the elongate holder 121. However, in alternativeembodiments other knife mounting and cutting arrangements may be used.For example, the knife may be disposed in a gap between two holder partsand reciprocally slidable, forwardly and rearwardly, in the gap, thesliding motion being between a forward projecting cutting position and arearward recessed non-cutting position. Known form, fill and sealmachines have a variety of different cutter arrangements and the heatseal device employed in the present invention has utility with thesevarious machines.

The lower portion of the knife 112 is received in an elongate recess 130in the elongate holder 121 and securely fixed therein. The cuttingaction of the knife 112 is progressive, so that initially onelongitudinal end 122 of the knife 112 first contacts the anvil 116 andsubsequently the contact point progresses along the cutting edge 120 ofthe blade 118 towards the other longitudinal end 124 of the knife 112.

To achieve such progressive cutting action, as shown in FIGS. 3 and 5,the knife 112 is mounted at an angle β to the longitudinal direction ofthe elongate holder 121. The cutting edge 120 of the blade 118 is groundso as to be parallel to the plane of the knife 112. Typically, the angleβ is 2 degrees.

A heat seal device is located on the elongate holder 121 on opposedsides of the knife 112. The heat seal device comprises a pair ofelongate pressure strips 126, 128.

The elongate pressure strips 126, 128 are parallel to the knife 112, andaccordingly the elongate pressure strips 126, 128 are also mounted at anangle β to the longitudinal direction of the elongate holder 121. Theknife 112 and the pressure strips 126, 128 are therefore inclined at theangle β to the longitudinal sides of the elongate holder 121 which isorthogonal to the longitudinal direction L. Thus, when the longitudinaldirection is oriented vertically, knife 112 and the pressure strips 126,128 inclined at the angle β to the horizontal.

The knife 112 and the pressure strips 126, 128 stand proud of themounting surface 138 of the elongate holder 121. Each pressure strip126, 128 extends along a respective side of the knife 112. Each pressurestrip 126, 128 comprises an elongate bar mounted for outward or inwardsliding movement in a slot 127, 129 in the elongate holder 121. Theoutward (indicated by the direction O in FIG. 4) or inward (indicated bythe direction I in FIG. 4) sliding movement can vary the distance anouter edge 131 of the elongate bar 126, 128 projects from the elongateholder 121. Each elongate bar 126, 128 is rigid, and typically iscomposed of a metal such as stainless steel. The elongate bar 126, 128has a thickness of from 1.5 to 2.5 mm. The outer edge 131 of theelongate bar 126, 128 has a convex cross-section, which is typicallyarcuate, for example the arcuate cross-section having a radius of from0.75 to 1.25 mm.

In the illustrated embodiment, the anvil 116 has a front surface 160formed with a pair of recessed channels 162, 164. Each channel 162, 164is aligned with and complementarily shaped with the outer edge 131 of arespective elongate bar 126, 128. Accordingly, as described below,during the heat sealing action the plural layers of the film material tobe sealed are pushed into the channels 162, 164 by the respectiveelongate bars 126, 128, which are at least partly received in thechannels 162, 164, to form an arcuate hermetic seal.

Alternatively, the front surface 160 of the anvil 116 may be planar.

A biasing element 133, 135 is located within the slot 127, 129 andengages an inner edge 137, 139 of the elongate bar 126, 128. The biasingelement 133, 135 comprises an elongate strip of elastic resilientmaterial, such as an elastomeric polymer. The elongate strip 133, 135 ofelastic resilient material has an upper surface 147, 149 which mateswith the inner edge 137, 139 of the elongate bar 126, 128. Preferably,the elongate strip 133, 135 of elastic resilient material has a circularcross-section.

The biasing element 133, 135 biases the elongate bar 126, 128 outwardlyof the slot 127, 129. However, additionally each elongate bar 126, 128is captive in the respective slot 127, 129 in the elongate holder 121.The elongate bar 126, 128 has a first coupling element 141, 142 locatedat each longitudinal end 143, 145 of the elongate bar 126, 128 whichcouples with a respective second coupling element 146, 148 located ateach longitudinal end 150, 152 of the slot 127, 129. The first andsecond coupling elements 141, 146; 142, 148 retain the elongate bar 126,128 captive in the elongate holder 121. In the illustrated embodiment,the first coupling element 141, 142 comprises a male element and thesecond coupling element 146, 148 comprises a channel extending along thesliding direction, indicated by the arrows O-I) of the elongate bar 126,128.

As the rotary contact progresses, the whole width of the flattened tube114 is not cut through simultaneously, but instead point contact of theknife blade 118 transitions across the tube 114 as the rotary actionprogresses.

The anvil 116 is a heated block incorporating an electrical resistanceheater 117. The heater may alternatively be in the elongate holder 121,or both the holder 121 and the anvil 116 may include a respectiveelectrical resistance heater 117. When the elongate pressure strips 126,128 are pushed against the anvil 116, the pressure strips 126, 128 urgethe flattened tube 114 against the heated anvil 116 so that transversehermetic heat seals 132, 134 are formed in the flattened tube 114 onopposite sides of the transverse cut 136 made by the knife 112.

Each pressure strip 126, 128 is pressed against the heated anvil surfacethereby simultaneously heat sealing together opposed sides of theflattened tube 114 to form an elongate transverse hermetic seal 132, 134in the vicinity of each cut end of the flattened tube 114. During thepressing action, each elongate bar 126, 128 slides rearwardly in therespective slot 127, 129 against the bias of the biasing element 133,135 within the slot 127, 129, but the outer edge 131 remains proud ofthe mounting surface 138. The pressure strips 126, 128, compressedagainst the bias of the biasing elements 133, 135 ensure uniform highpressure along the flattened tube 114 which forms highly and uniformlybonded hermetic seals 132, 134 of predetermined narrow width. Afterrelease of the sealing pressure, the pressure strips 126, 128 are urgedoutwardly again by the outward bias of the biasing elements 133, 135 soas return to their original rest position.

The pressure strips 126, 128 locally press the film material of the tube114 against the heated anvil 116 to form the two spaced hermetic seals132, 134 of defined width determined by the profile of the outer edge131 of the elongate bar 126, 128. During the sealing action, the plurallayers of the film material of the tube 114 are pushed into the channels162, 164 by the respective elongate bars 126, 128 to form an arcuatehermetic seal. Alternatively, if the anvil 116 has a planar surface 160then planar hermetic seals are formed.

The elongate pressure strips 126, 128 are parallel to the knife 112 andso the entire assembly of the knife 112 and the elongate pressure strips126, 128 on opposite sides thereof is mounted at an inclination to thelongitudinal direction of the elongate holder 121.

The provision of elongate pressure strips 126, 128 of rigid materialsuch as metal which are urged against a rigid heated anvil 116, whichmay have a complementarily profiled channelled surface or a planarsurface, provides the advantage of a high strength seal of minimumwidth. The pressure strips 126, 128 can exert a high pressure over asmall surface area, providing an enhanced heat seal as compared toproviding a lower pressure seal over a greater width. Therefore anarrower heat seal can provide improved hermetic performance anddurability as compared to a wider seal. The elongate pressure strips126, 128 are biased by concealed elastic resilient material, which isnot subject to external contact and so is safely retained within theslots 127, 129, and is not subjected to excessive wear.

Typically, the entire width of the assembly of the knife 112 and theelongate pressure strips 126, 128, all inclined to the longitudinaldirection of the elongate holder 121, is 8 mm, whereas in the knowndevice the entire width of the assembly of the knife 12 and the heatseal devices 26, 28, all parallel to the longitudinal direction of theelongate holder 21 is 20 mm.

The result of this change of structure and orientation of the knife isshown in FIG. 5.

FIG. 6 shows two adjacent packages 200, 202 which have been separated bya cut formed by the knife 112. Each package 200, 202 has a cuttransverse edge 204, 206 which is inclined at the angle β (exaggeratedin the Figure) to the longitudinal direction of the package 200, 202.The angle is sufficiently small that it would not ordinarily be noticedby the consumer. A heat seal, forming a hermetic seal 208, 210, isprovided at the end of each package 200, 202. An unsealed endmostportion 212, 214 adjacent to the cut transverse edge 204, 206 has awidth corresponding to one half of the knife thickness. Therefore theunsealed endmost portion 212, 214 has a typical thickness of 0.5 to 1.5mm, most typically 1 mm, which can be compared to a typical thickness of2.5 mm of the corresponding unsealed endmost portion produced by theknown device of FIGS. 1 to 3.

Therefore for each package produced in accordance with this embodimentof the invention there is a typical total film material saving of 3 mmin length without having any impact of the security of the heat seal.

This material saving is achieved by reducing the amount of unsealedmaterial at the ends of the packages that has no functional purpose withrespect to forming a hermetic seal.

In addition, the heat seal can be narrower than known heat seals byusing the specific pressure strips against the heated anvil, providingeven greater packaging material savings. Typically, the heat seal has awidth of from 1 to 4 mm, optionally 1 to 2 mm.

Such a film material saving has potentially enormous impact on highvolume production of products such as snack foods.

The Applicant and its related companies form part of one of the largestsnack food companies in the world, and it is estimated that thispackaging material saving cumulatively amounts to a global cost savingin packaging material of many tens of millions of dollars per annum,and, importantly, a saving of approximately 16 thousand tonnes of carbondioxide production per annum. This invention therefore may yield verysignificant reductions in the carbon footprint of the packaging of awide variety of products, particularly snack foods.

It will be clear to a person skilled in the art that the angle anddimensions exemplified above are merely indicative of an angle size anddimensions that may be used in accordance with the present invention,and that these parameters may be varied depending upon a number offactors, including package size, shape and dimensions.

The jaw device and method may be used to produce primary packages of avariety of products, of which snack foods are only a preferred example.The jaw device and method may also be adapted to produce secondarypackages, for example multi-pack packaging.

As described above for the known device, in the device of the inventionplural knives may be mounted about a common shaft disposed along therotational axis and mutually angularly separated, so that for each cycleof rotation of the common shaft, plural cuts are made by respectiveknives, and corresponding plural packages are separated by the cuttingaction for each rotational cycle of the shaft. Plural anvils would becorrespondingly provided.

In an alternative embodiment, the jaw device may have a translationalaction rather than a rotary action, and either or both of the elongateholders for the knife and the anvil may be translationally reciprocated.

Other modifications to the embodiment of the invention disclosed hereinwill be apparent to those skilled in the art.

1. A packaging apparatus including a cutting device, the cutting devicecomprising an elongate holder, an elongate knife having an elongatecutting edge, and a heat seal device located on the elongate holder onopposed sides of the knife, the heat seal device comprising a pair ofelongate pressure strips projecting outwardly from the elongate holder,each pressure strip extending along a respective side of the knife,wherein each pressure strip comprises an elongate bar mounted forsliding movement in a respective slot in the elongate holder, thesliding movement varying the distance an outer edge of the elongate barprojects from the elongate holder, and a biasing element within therespective slot, the biasing element engaging an inner edge of theelongate bar and arranged to bias the elongate bar outwardly of theslot.
 2. A packaging apparatus according to claim 1 wherein the elongatebar is rigid.
 3. A packaging apparatus according to claim 1 or claim 2wherein the outer edge of the elongate bar has a convex cross-section.4. A packaging apparatus according to claim 3 wherein the convexcross-section is arcuate.
 5. A packaging apparatus according to claim 4wherein the arcuate cross-section has a radius from 0.75 to 1.25 mm. 6.A packaging apparatus according to any foregoing claim wherein theelongate bar has a thickness of from 1.5 to 2.5 mm.
 7. A packagingapparatus according to any foregoing claim wherein the elongate bar iscomposed of a metal.
 8. A packaging apparatus according to claim 7wherein the metal is stainless steel.
 9. A packaging apparatus accordingto any foregoing claim wherein the elongate bar is captive in theelongate holder.
 10. A packaging apparatus according to claim 9 whereinthe elongate bar has a first coupling element located at eachlongitudinal end of the elongate bar which couples with a secondcoupling element located at each longitudinal end of the slot, the firstand second coupling elements retaining the elongate bar captive in theelongate holder.
 11. A packaging apparatus according to claim 10 whereinthe first coupling element comprises a male element and the secondcoupling element comprises a channel extending along the slidingdirection of the elongate bar.
 12. A packaging apparatus according toany foregoing claim wherein the biasing element comprises an elongatestrip of elastic resilient material.
 13. A packaging apparatus accordingto claim 12 wherein the elastic resilient material comprises anelastomeric polymer.
 14. A packaging apparatus according to claim 12 orclaim 13 wherein the elongate strip of elastic resilient material has anupper surface which mates with the inner edge of the elongate bar.
 15. Apackaging apparatus according to any one of claims 12 to 14 wherein theelongate strip of elastic resilient material has a circularcross-section.
 16. A packaging apparatus according to any foregoingclaim wherein the elongate knife is mounted on and projects outwardlyfrom the elongate holder.
 17. A packaging apparatus according to anyforegoing claim wherein the holder is mounted on a mounting supportadapted to rotate about a rotational axis, the knife is planar, theelongate cutting edge is parallel to the plane of the knife and theplane of the knife is inclined to the rotational axis.
 18. A packagingapparatus according to claim 17 wherein the cutting edge extends along acentre of the knife.
 19. A packaging apparatus according to claim 18wherein the knife has a thickness of from 1 to 3 mm.
 20. A packagingapparatus according to any foregoing claim further comprising an anvilmounted in opposition to the elongate holder, so that the elongateholder and the anvil comprise opposed jaws of a jaw device, the anvilhaving a reaction surface for the cutting action of the knife and forthe pressure strips.
 21. A packaging apparatus according to claim 20wherein the holder is mounted on a mounting support adapted to rotateabout a rotational axis, the elongate cutting edge is parallel to theplane of the knife and the plane of the knife is inclined to therotational axis and the knife and anvil are mutually arranged so that asthe knife rotates by rotation of the elongate holder, the cutting edgeof the knife progressively contacts the reaction surface with a contactpoint therebetween moving longitudinally along the cutting edge.
 22. Apackaging apparatus according to claim 20 or claim 21 wherein the anvilcomprises a heater for heating the reaction surface.
 23. A packagingapparatus according to any foregoing claim adapted for forming pillowpacks of film material.
 24. A method of making packages, the methodcomprising the steps of: a. providing a flattened tube of packagingfilm; b. providing a cutting device mounted in opposition to an anvil sothat the cutting device and the anvil comprise opposed jaws of a jawdevice, the cutting device having an elongate knife with an elongatecutting edge, a pair of elongate pressure strips projecting outwardlyfrom an elongate holder, each pressure strip extending along arespective side of the knife, wherein each pressure strip comprises anelongate bar mounted for sliding movement in a respective slot in theelongate holder, the sliding movement varying the distance an outer edgeof the elongate bar projects from the elongate holder, and a respectivebiasing element within the slot, the biasing element engaging an inneredge of the elongate bar and arranged to bias the elongate bar outwardlyof the slot, and the anvil having a reaction surface for the cuttingaction of the knife and for the pressure strips, at least the reactionsurface for the pressure strips being heated; c. locating a portion ofthe flattened tube between the cutting device and the anvil; d.relatively moving the cutting device and the anvil together; e. cuttingthrough the portion of the flattened tube between the cutting device andthe reaction surface of the anvil by the cutting action of the knife;and f. pressing the pressure strips against the heated reaction surfacethereby simultaneously heat sealing together opposed sides of theflattened tube to form an elongate transverse hermetic seal in thevicinity of each cut end of the flattened tube, during the pressingaction each elongate bar sliding rearwardly in the respective slotagainst the bias of the biasing element within the slot.
 25. A methodaccording to claim 24 wherein the biasing element comprises an elongatestrip of elastic resilient material.
 26. A method according to claim 25wherein the elastic resilient material comprises an elastomeric polymer.27. A method according to any one of claims 24 to 26 wherein theelongate bar is rigid.
 28. A method according to any one of claims 24 to27 wherein the outer edge of the elongate bar has a convexcross-section.
 29. A method according to claim 28 wherein the convexcross-section is arcuate.
 30. A method according to claim 29 wherein thearcuate cross-section has a radius from 0.75 to 1.5 mm.
 31. A method anyone of claims 24 to 30 wherein the elongate bar has a thickness of from1.5 to 2.5 mm.
 32. A method according to any one of claims 24 to 31wherein the cut edge of each package is 0.5 to 1.5 mm from the hermeticseal.
 33. A method according to claim 32 wherein the cut edge of eachpackage is about 1 mm from the hermetic seal.
 34. A method according toany one of claims 24 to 33 wherein the hermetic seal has a width of from1 to 4 mm.
 35. A method according to claim 34 wherein the hermetic sealhas a width of from 1 to 2 mm.
 36. A method according to any one ofclaims 24 to 35 wherein the packages are pillow packs of film material.37. A method according to claim 36 wherein the packages contain snackfood.